UN-AUTHORIZED SUBSCRIPTION

I just got a text message to say I owe them R150 for subscribing to Showmax, which I've never did and i don't even know what that is as am having a standard account that am even paying in advance, I phoned them this morning to ask what is going on? they telling that i've subscribed to that show-max that why i owe them I tried to explain but they won't even listen to me.The consultant just told me it's the subscription that I must pay. Why would on earth must I pay for something i don't even know off?? can someone please help me here.